It's no secret that people get SAD in winter. You may recognize the symptoms in yourself or someone close to you: a pervading sense of blues and anxiety; lack of energy; sleepiness and wanting to stay in bed; little interest in your social life; difficulty concentrating; weight gain.
“In seasonal affective disorder, the depressive symptoms are present only during the winter or become worse during the winter, when nights are longer,” says sleep specialist Meir H. Kryger, MD, a professor at the Yale School of Medicine and lead author of Elsevier's Principles and Practice of Sleep Medicine (Elsevier, 2012). “In addition to the sadness, people will often put on a great deal of weight due to changes in the levels and timing of the release of hormones that affect appetite. SAD is therefore not considered to be a separate disease, but a variant of depression. A milder variation of the disorder has been described as Subsyndromal Seasonal Affective Disorder, or SSAD, in which the symptoms of depression are less severe.”
We asked Dr. Kryger about why SAD affects us and how to feel better:
Everyday Health: What exactly is Seasonal Affective Disorder?
Dr. Kryger: Seasonal affective disorder is believed to be a wintertime recurrence or worsening of depression. The symptoms of depression include
Are women impacted more than men – how so?
Women are more likely to be diagnosed with SAD, and this may simply reflect the increased susceptibility of women to depression. This was studied in Alaska, for example, by the University of Alaska Anchorage. About 9 percent of the population seems to have SAD and the risk of having SAD is 50 percent higher in females than males. SAD was more common in younger compared to older people.
At what time of year are people most affected?
The disorder seems to recur as light exposure starts to decrease with the shortening of days in the late fall. Days are shortest (and nights longest) the third week of December in the Northern Hemisphere and during the third week of June in the Southern Hemisphere.
What regions of the world are most affected?
The closer geographically one lives to the North and South Poles, the greater the reduction in daylight and the more likely that SAD will be present. However, there is some data that suggests that some populations (for example, people of Icelandic descent) may be protected from developing SAD even though they live at latitudes where one would expect many people to have SAD.
Why do shorter days and less light impact human hormones?
Melatonin is a hormone that is produced in the pineal gland in the brain when it is dark outside. However, an increased level of melatonin is not the only explanation for SAD. When days are shorter and nights longer, the circadian system has a phase delay. In other words, the functions and timing of hormone secretions during sleep that are controlled by the circadian system occur later. The circadian system needs exposure to sunlight to resynchronize the many functions of the body that are related to time. In addition, even though one might expect a longer night would increase the amount and quality of sleep time, there is a reduction in percent of time in bed asleep. It also takes longer time to fall asleep; there is poorer sleep quality, and overall less sleep time in winter. The combination of factors can impact several hormone systems involved in appetite control and metabolism as well.
Why do people crave more carbohydrates and experience weight gain?
The resulting circadian desynchrony and shorter sleep time may affect levels of hormone that control appetite (leptin and ghrelin) and may negatively affect the body's metabolism and response to the hormone insulin (effects on insulin sensitivity). The result of the changes in the levels and timing of hormones result in weight gain. That's why people with SAD typical gain weight during the winter months.
What characterizes SAD as a different disorder from depression or MDD (major depressive disorder)?
SAD is by definition seasonal. However, it could be that SAD is not a separate entity at all but that reduced exposure to sunlight precipitates or worsens depression in susceptible people. Recent research suggests that the susceptibility may be related to genetic variations in the coding for a pigment called melanopsin. This pigment is light sensitive and is found in specialized cells in the eye that are believed to play a role in resetting the biological (circadian) clock in the brain.
Is there any evidence that this disorder affected our ancestors or is it a modern disorder?
This is likely not a modern disorder and has likely affected people living in northern climes well before modern times. Seasonality is found throughout biology. Hibernation and the seasonality of reproduction of some species are two examples.
What are the main treatments?
Bright light: A thirty minute exposure to bright light (natural sunlight or with a “light box”) in the morning through the winter season, or starting just before the person normally develops SAD symptoms, can be effective in treating SAD.
Blue light: It has also been suggested by medical researchers that a lower intensity and duration of exposure to blue enriched light can also be effective. An example of what such a blue enriched lamp looks like can be found in The iGuide to Sleep.
Medicine: Antidepressants are a modality of treatment recommended for SAD. Although there is evidence supporting the use of antidepressant in severe depression, the quality of the evidence supporting the use of the most widely used antidepressants specifically for SAD is not impressive.
What is your advice to those who may be dealing SAD?
1. Speak to your physician or healthcare provider to make sure you have SAD. You may need medication or other treatment.
2. Around October, as the days become shorter, make an effort to be exposed to sunlight in the morning. However, never stare directly at the sun!
3. If it is dark in the morning, consider obtaining one of the special lamps marketed for this purpose. The blue enhanced lamps may be more effective at lower intensity.
4. A 30-minute exposure to natural sunlight or an artificial lamp should be adequate to prevent SAD symptoms.
5. If the symptoms of depression do not improve, contact your health care provider.